Principle

One step pregnancy test utilize the principle of Immunochromatography, A unique two site immunoassay on a membrane. As the test sample flows through the membrane assembly of the dipstick, the colored anti-hcG-colloidal gold conjugate complexes with the hcG in the sample.

This complex moves further on the membrane to the test region where it is immobilized by the anti-hcG coated on the membrane leading to formation of a purple colored band which confirm a positive test result. Absence of this colored band in the test region indicate a negative test result.

The unreacted conjugate and unbound complex if any move further on the membrane and are subsequently immobilized by the anti-rabbit antibodies coated on the membrane at the control region, forming a purple band. This control band serves to validate the test results.

Specimen: urine sample

Requirements

1. Each individual pouch contains.
2. DIPSTICK: membrane assembly Predispensed with anti-HCG antiserum and anti-rabbit antiserum at the respective regions.
3. Desiccant pouch.
4. Package insert.

Procedure

1. Collect urine specimen in a clean test tube. Ensure that only sufficient quantity of the specimen is collected to allow submerging the red area of the dipstick.
2. Bring the sealed pouch to room temperature, open the pouch and remove the dipstick. Once opened, the dipstick must be used immediately.
3. Dip the red area of the dipstick in the urine specimen submerging only the red area.
4. Observe for the release of the colloidal gold complex on the membrane. This would be seen as a purple moving front on the membrane and could take 10 to 15 seconds to appear depending upon the sample.
5. Remove the dipstick and place horizontally on a flat surfaces Alternatively the dipstick may be left to stand in the specimen for the entire duration of the test ensuring only the red area is left submerged in the specimen.
6. At the end of five minutes read the results as follows

Clinical significance

Human chronic gonadotropin (hcG), a glycoprotein hormone secreted by viable placental tissue during pregnancy, is excreted in urine approximately 20 days after the last menstrual period. The levels of hcG rise rapidly reaching peak levels after 60-80 days. The appearance of hcG in urine soon after conception and its rapid rise in concentration makes it an ideal marker for the early detection and confirmation of pregnancy.

However elevated hcG levels are frequently associated with trophoblastic and non-trophoblastic neoplasms and hence these condition should before a diagnosis of pregnancy can be made. One step pregnancy test detects the presence of hcG in urine specimen, qualitatively, at concentration as low as 10mlU/ml in less than five minutes.

Reference

KIT USED – ORCHID BIOCHEMICAL SYSTEM

                  CLUE HCG